package problem149_Max_Points_on_a_Line;

import java.util.HashMap;
import java.util.Map;

public class Solution {
	public int maxPoints(Point[] points) {  
        if (points.length < 3) return points.length;  
        int max = 0;//用于返回的结果，即共线点的最大个数  
        Map<Double, Integer> map = new HashMap<Double, Integer>();//保存同一个斜率的点的个数  
        for (int i = 0; i < points.length; i++) {//以每一个点为固定点  
            map.clear();  
            int duplicate = 1;//记录跟固定点重合的个数  
            for(int j = 0 ; j < points.length; j++){//遍历其他点，求其与固定点之间的斜率  
                if (i == j) continue;//如果是自己，跳过  
                double slope = 0.0;//斜率  
                if (points[i].x == points[j].x && points[i].y == points[j].y) {//如果跟固定点重合  
                    duplicate++;  
                    continue;  
                } else if (points[i].x == points[j].x) {//如果跟固定点在同一条竖线上，斜率设为最大值  
                    slope = Integer.MAX_VALUE;  
                } else {//计算该点与固定点的斜率  
                    slope = 1.0 * (points[i].y - points[j].y) / (points[i].x - points[j].x);  
                }  
                map.put(slope, map.containsKey(slope) ? map.get(slope) + 1 : 1);  
            }  
            //更新最优解  
            if (map.keySet().size() == 0) {//如果map为空  
                max = duplicate > max ? duplicate : max;  
            } else {  
                for (double key : map.keySet()) {  
                    max = Math.max((duplicate + map.get(key)), max);   
                }  
            }  
        }  
        return max;  
    }  
}

class Point {
   int x;
   int y;
   Point() { x = 0; y = 0; }
   Point(int a, int b) { x = a; y = b; }
}